1. Field of the Invention
The invention relates to an orthopedic surgical device and, more particularly, to a device to be used in bone lengthening by bone fracture and gradual distraction of callus.
2. Description of the Related Art
In the 1900s, medical science began experimenting with bone lengthening techniques. Early bone lengthening procedures proved ineffective due to a variety of factors, such as complication by edema, skin necrosis, infection, angular deviation, and delayed ossification of the expanded segment. As a result, medical practitioners abandoned attempts at bone lengthening in favor of practices of cutting complimentary bones to obtain symmetry or using prostheses to compensate for bone length disparity.
Then in the 1950s, Dr. Gavril A. Ilizarov, a Russian physician, developed what is now referred to as the "Ilizarov Technique" for bone lengthening. In the Ilizarov Technique, bones are lengthened by severing the cortex of a bone to be lengthened while minimizing damage to the periosteum and the medullary cavity, and then very gradually separating the separated cortex ends as new bone is generated in the distraction gap. Since the origins of the Ilizarov Technique, considerable advances have been made to techniques and processes of bone lengthening in general keeping with the techniques of Ilizarov.
The original Ilizarov Technique was, in particular, directed primarily to lengthening bones in the leg. In the original Ilizarov Technique, pins were placed through the skin into the bone, bone between the pins was partially cut, and then gradually the pins were pulled apart over a period of many weeks. As a result of this slow expansion, the bone had the opportunity to regenerate, filling in the gradually enlarging gap.
Practice of the Ilizarov Technique is presently limited to only certain cases of bone deformity where lengthening is necessary. Many birth defects involve the skull and facial skeleton. Those birth defects often result from a local growth disturbance in that area. An example of such a birth defect is a forehead which does not grow forward sufficiently to accommodate growth of the child. Those defects can lead to an increase in pressure on the brain as the brain grows and is restricted from further growth by the forehead. Development delays can result from this condition. The typical treatment presently followed in these cases involves a technique, different from the Ilizarov Technique, where bones are cut and moved to another location. This particular technique unfortunately has certain limitations because, with subsequent growth of the patient, in particular where the patient is a growing child, the deformity may recur. In attempts to compensate for the possibility of recurrence of the deformity in these patients, practitioners oftentimes move bones farther than necessary to compensate for expected growth, or other complications result from the technique.
A more recent form of treatment for bone deformities in the skull and facial skeletal region utilizes the Ilizarov Technique. To date, the Ilizarov Technique is known to have been applied to the skull and facial skeletal bones at medical centers in New York and Mexico City. It is believed that the only use to date of the technique in that regard is with children having one side of the jaw which does not grow forward to the extent of the growth of the other jaw side. In the treatment of this particular deformity by means of the Ilizarov Technique, pins are placed through the skin into the jaw, the jawbone is severed, and the severed parts of the jawbone are gradually moved apart, allowing time for the space between the severed parts to fill in with new bone. Employment of the Ilizarov Technique in this manner has certain adverse effects including long stretched out scars that are left in the facial skin from the pins. Additionally, the technique in this instance requires a cumbersome external device, which must be worn by the patient for up to six to eight weeks.
An example of the type device used in current practice of the Ilizarov Technique in these cases is shown in U.S. Pat. No. 5,147,358 to Daniel J. Remmler. This patent, issued in 1992, teaches a skull distraction and fissioning apparatus and method implementing multiple mini-fixation plates attached to a cranial-facial skeleton. As set forth therein, the apparatus and method are for surgically attaching the plates to the skull and then monitoring skull expansion, all as set forth and shown therein. In particular, the Remmler device and method require that plates be surgically attached to the skull through overlying soft skin tissues. As with the other prior art techniques described above for similar treatments or for use with the Ilizarov Technique, use of the device and method of Remmler result in traumatic scarring, like that which resulted from the use of pins in the original Ilizarov Technique.
The present invention exhibits significant improvement in the prior devices and methods for use in practice of the Ilizarov Technique and, in particular, when that technique is used in connection with the skull and facial skeletal bones. The invention provides a device and method of cranial-facial bone expansion utilizing a drive expansion plate system, internally disposed with respect to the skin, having a drive which may be actuated from a single location, which location is remotely disposed from the plate system. Because the plates are mounted internally to the skull with respect to the skin and the actuation mechanism for the drive is remotely disposed from the plates, the invention provides a device and method suitable for practice of the Ilizarov Technique, which device and method substantially reduce, or even eliminate, traumatic scarring and dispose of the necessity that a cumbersome structure be worn by the patient for an extended period.